1. Field of the Invention
The invention is directed to an improved high-pressure pump for a fuel injection system of an internal combustion engine.
2. Description of the Prior Art
One high-pressure pump known from German Patent Disclosure DE 198 44 272 A1 employs a rotationally driven drive shaft, which has a shaft portion embodied eccentrically to the axis of rotation of the drive shaft. A polygonal ring is rotatably supported on the eccentric shaft portion. The high-pressure pump has at least one pump element, with at least one pump piston driven in a reciprocating motion at least indirectly by the drive shaft via the ring. The ring, on its circumference, has flat faces, corresponding in number to the pump elements, on which faces the pump pistons rest at least indirectly, for instance via a tappet. In operation of the high-pressure pump, heavy loads on the ring and the pump pistons or tappets, especially high pressures per unit of surface area, occur. Moreover, sliding motions can occur between the ring and the pump pistons or tappets. Lubricating the contact region between the ring and the pump pistons or tappets is done by means of the fuel present in the interior of the high-pressure pump housing. Particularly at high fuel temperatures, however, the lubrication provided by the fuel is no longer sufficient, so that severe wear of the ring and/or the pump pistons or tappets occurs, which finally can cause failure of the high-pressure pump.